Fix public repository access in GitDagBundle

[amoghrajesh]

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Was generative AI tooling used to co-author this PR?

• No

Problem

#59084 broke public repository support in GitDagBundle. When we tried to configure public repositories without authentication, the bundle initialization would fail with and error like this:

AirflowNotFoundException: The conn_id git_default isn't defined

This was affecting all users using public repos with dag bundles.

The root cause was that the linked PR changed error handling to reraise all GitHook creation exceptions to provide clearer error messages. However, this broke the valid use case where users configure a public repo with explicit repo_url which lead to Githook creation failing error being reraised due to which the entire bundle would be killed, making dag bundles unusable. In other words, no dags would be seen on the Airflow UI.

Fix

The fix is to make the git connection optional when repo_url is explicitly provided:

• If repo_url is NOT provided: Connection is required (to get the repo URL) and exception if any, is raised.
• if repo_url IS provided: Connection is optional and exception is caught, bundle continues without authentication

This is a middle ground which allows public repositories to work without any connection configuration, while still maintaining clear error messages that the linked PR fixed earlier.

Testing

Configure the git bundle:

export AIRFLOW__DAG_PROCESSOR__DAG_BUNDLE_CONFIG_LIST='[{"name": "git_repo", "classpath": "airflow.providers.git.bundles.git.GitDagBundle", "kwargs": {"tracking_ref": "main", "subdir": "examples", "repo_url": "https://github.com/AmFlint/test-af.git"}}]'

Earlier this would be seen:

After the fix, this is what we see:

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